This invention relates to an improved method and system of positioning a boring mechanism in a stern tube, such as in ship-building, and more particularly, to such a method and system employing a laser beam to accomplish the centering of the boring mechanism in the tube.
In the prior art, there are various methods and systems for centering a boring bar within a stern tube. For example, one prior art method employs the following steps. First, a center point is established on both ends of the stern tube. Then, a circle of a predetermined desired radius is marked from the center point of the two ends of the stern tube. Thereafter, a deflection amount of the bar at the marked position is calculated from a deflection curve premeasured on a surface plate. Then, bolt and bearings for supporting the bar within the tube are adjusted corresponding to the calculated deflection amount. The deflection amount at the middle of the bar is revised based on the above deflection curve through a dial gauge or the like set to an intermediate reading.
Unfortunately, there are many difficulties and deficiencies in the prior art methods and systems, such as those above discussed. For example, when the boring bar is set up, it is difficult to measure the deflection amount from a marking line so that precise accuracy is not obtained. Moreover, for large dimension tubes, even if an operator enters the stern tube, longitudinal slippage is barely measurable. Also, it is necessary to prepare the pre-measured deflection curve on the surface plate of every ship-building. Furthermore, there is no method or system existing in the art which would insure the retaining of the center position of the boring bar after revising or correcting the deflection. Thus, slippage from the center line of machining is difficult to detect and correct.
Up to now, no effective and suitable counter measure has been developed.